Add error_threshold parameter, add error check after load

Signed-off-by: Andrey Berezin <a.berezin@yadro.com>

src/frostfs_testlib/load/load_report.py

@@ -154,6 +154,7 @@ class LoadReport:
         <tr><th colspan="2" bgcolor="gainsboro">Errors</th></tr>
         {per_node_errors_html}
         {self._row("Total", f"{total_errors} ({total_errors/total_operations*100.0:.2f}%)")}
+        {self._row("Threshold", f"{self.load_params.error_threshold:.2f}%")}
         </tbody></table><br><hr>
         """